1. Field of the Invention
The present invention relates to an electronic camera which is provided with an electronic flash and an LCD monitor and uses a battery as a power supply, and to a battery voltage controlling method employed therein.
2. Description of the Background Art
In recent years, electronic cameras in which an image formed by a CCD imager is signal-processed and stored in a recording medium, such as a flash memory, are in common use. In particular, the type integrally equipped with various accessories, such as an electronic flash device and an LCD monitor, commercially preferred.
Typically, this electronic camera uses a battery, such as a dry cell and a secondary cell, as a power supply. Thus, desirably, the load on the battery is reduced as much as possible to contemplate longer life time of the battery itself and variations of battery voltage are also suppressed. With an electronic camera equipped with an electronic flash device, an LCD monitor and the like, however, the load of the electronic flash device, LCD monitor and the like which receive power supplied from the battery as well as the inherent load of the camera portion, such as a CCD imager and a signal processing circuit, poses a significant problem. For the electronic flash device, for example, a large current is required to flow therethrough when the discharge tube of the electronic flash device emits light. Thus, when the capacitor for the electronic flash is charged during either light emission or non-light emission in preparation for the next light emission, a large current will flow from the battery and cause a large load. For the LCD monitor also, a predetermined driving voltage needs to be constantly applied while displaying an image.
As described above, when the load of the electronic flash device and LCD monitor as well as the inherent load of the camera portion is placed on the battery, battery voltage will significantly drop. When a sufficient amount of electric charge remains in the battery, a slight, additional application of load would not cause any particular problems. When a small amount of electric charge remains in the battery, however, the output voltage will be reduced without any application of load, as compared with the case where a sufficient amount of electric charge remains in battery. If a large load is applied in this condition, a large drop in battery voltage is more readily caused.
The camera portion includes various types of integrated circuits and microcomputers for analog and digital processing. Thus, when battery voltage has significantly dropped, it falls below the lower limit at which the integrated circuits and microcomputers can properly operate, and proper signal processing might not be achieved.